Geologic Formations and their Water-bearing Characteristics

Permian System

Leonardian Series

Permian rocks of Leonardian age are the oldest rocks exposed at the surface in Reno County. Included are the Wellington shale (not exposed), Ninnescah shale, Stone Corral dolomite, and Harper sandstone. These rocks are present in northeastern Reno County on the north side of the Little Arkansas River, in the upland area of southeastern Reno County, and along the Ninnescah River in south-central Reno County.

Wellington Shale

Although the Wellington shale does not crop out in Reno County, the formation underlies younger deposits in the county. Test holes in the Arkansas and Little Arkansas River valleys encountered the Wellington shale below Cenozoic deposits, and the formation underlies younger Permian and other deposits in upland areas in south-central Reno County.

The Wellington is composed chiefly of silty gray shale. The upper boundary of the formation is marked by the Milan limestone member, which is an impure limestone about 1 foot thick. The thick Hutchinson salt member lies about 300 feet below the top of the formation. The Carlton limestone member occurs a short distance below the Hutchinson salt member. Red and green shales predominate below the Carlton limestone member, and the Hollenberg limestone member lies about 35 feet above the base of the formation. The total thickness of the formation is about 700 feet. The Wellington shale yields no water to wells in Reno County.

Ninnescah Shale

The Ninnescah shale is the oldest formation exposed in the county. The formation is composed of alternating beds of red and light-gray shale, silty shale, and siltstone. Small veins of gypsum are present in a few exposures.

The Ninnescah shale conformably overlies the Wellington shale. The Ninnescah crops out in the northeastern and in the southeastern and south-central parts of the county, where erosion by small streams has resulted in dissected topography typical of the formation. The best exposures are found along the forks of the Ninnescah River in Kingman and Reno counties, from which stream the shale derives its name. The average thickness of the formation is about 280 feet in that area.

The Ninnescah shale furnishes water to domestic and stock wells in the area of its outcrop and in an area north of Ninnescah River in south-central Reno County. The formation yields water from the weathered part of the shale, from crevices in the shale, and from sandstones. Water from the Ninnescah shale generally is highly mineralized (Fig. 17).

Stone Corral Dolomite

The type locality of the Stone Corral dolomite is in sec. 11, T. 20 S., R. 6 W., Rice County, about 10 miles north of Reno County. The formation is composed of dolomite, gypsum, and anhydrite. On the outcrop the formation is about 6 feet thick, the lower part being massive and the upper part slabby. Solution of the gypsum and anhydrite has caused thinning along the outcrop; the formation thickens west of the outcrop. In Reno County the Stone Corral dolomite crops out along the Ninnescah River in the south-central part of the county and in the northeastern part of the county.

The Stone Corral dolomite yields no water to wells in Reno County.

Harper Sandstone

The Harper sandstone conformably overlies the Stone Corral dolomite and is composed mainly of red siltstone and very fine grained silty sandstone. In south-central Kansas the average thick-ness of the formation is about 140 feet.

The Harper sandstone crops out in the south-central part of Reno County. The best exposures are in T. 25 S., R. 8 W., where the sandstone forms the hills along the Ninnescah River.

In the area of outcrop the Harper sandstone yields small supplies of highly mineralized water to domestic and stock wells.

Quaternary System

Pleistocene Series

The Pleistocene series in Kansas is divided into four main stages related to continental glaciation, and three main interglacial stages. Events in each of the periods of continental glaciation followed a cyclic repetition. Each of the cycles consists of a glacial and an interglacial interval or stage. The cycle in the marginal belt of a glaciated area is characterized by a period of downcutting in the valleys and some local deposition of sediments, followed by a period of deposition of coarser materials from outwash beyond the glacial limit, deposition of progressively finer-grained material as the glacier retreated, and finally the development of soil profiles over large areas where surface conditions were relatively stable.

Unconsolidated deposits of Pleistocene age unconformably overlie older deposits of Permian age in the greater part of Reno County. The deposits represent each of the four glacial stages.

Although deposits that represent all the glacial stages are present in Reno County and can be identified in the field and on logs of wells and test holes, it is difficult to map some of these units separately. On the geologic map (P1. 1) deposits of the Meade formation and the Crete, Loveland, and Peorian members of the Sanborn formation are all mapped as the Sanborn formation undifferentiated, even though these units can be identified in isolated outcrops and in most of the test-hole logs. Figures 8-11 give additional information on the distribution of certain Pleistocene units in the county.

Blanco Formation--Nebraskan and Aftonian Stages

The Blanco formation is composed of the (lower) Holdrege sand and gravel member and the (upper) Fullerton silt member, and represents the Nebraskan stage of the Pleistocene in Reno County. The formation unconformably overlies Permian rocks. The topography of the Permian surface at the beginning of the Pleistocene was an area having little relief. In the downcutting period of the Nebraskan Stage, deep broad channels were cut into the Permian rocks. These channels were filled during the middle and later parts of the Nebraskan Stage of the Pleistocene with deposits of the Blanco formation.

Holdrege member--Deposits of sand, gravel, and silt classified as the Holdrege member of the Blanco formation occur in deep buried channels in Reno County. One buried channel enters the area near the northwest corner of the county and trends nearly east halfway across the county, where it is joined by another buried channel from the north. From the junction of these two channels, the main buried channel trends southeast and leaves the county at about the middle of the east county line. The deposits of sand and gravel range in texture from fine sand to coarse gravel and contain some silt and clay. A large part of the sand and gravel was derived from Cretaceous and Permian material. In southwestern Reno County, another buried channel enters the area and trends eastward for a distance of about 10 miles and then turns south out of the county. Deposits in this channel are similar to those in the channels in northern Reno County. East of the point where the channel in southwestern Reno County trends south, there is an area in which deposits of the Blanco formation crop out. These deposits lie at a higher elevation than the deposits in the channels, but consist of sand, gravel, and silt similar to the channel deposits. A few cobbles of quartzite are found, some as much as 6 inches in diameter. The Holdrege member ranges in thickness from a featheredge to as much as 110 feet.

The Holdrege member yields no water to wells in the channel areas. Large quantities of water are available, but the water is highly mineralized and not suitable for domestic or industrial use. The deposits of the Blanco formation that crop out in south-central Reno County yield water of good quality to wells. A graphic presentation of analysis of water from the principal water-bearing formations is shown in Figures 17 and 18, and the saturated thickness of the Pleistocene deposits is shown in Figure 23.

Fullerton member--The Fullerton member of the Blanco formation overlies the Holdrege sand and gravel member. The Fullerton member is composed of tan alluvial silt. A zone of caliche accumulation found at many localities is suggestive of soil development during the Aftonian interglacial stage. Deposits of the Fullerton member ranging in thickness from 20 to 30 feet were penetrated in test holes in Reno County.

Wells do not produce water from the Fullerton member in Reno County, because the water is highly mineralized. Also, the Fullerton and the Holdrege members of the Blanco formation are overlain by younger Pleistocene deposits that yield large supplies of water of good quality to wells.

Meade Formation--Kansan and Yarmouthian Stages

The Meade formation in Reno County unconformably overlies the Blanco formation and Permian rocks. The formation is composed of a lower gravel member, the Grand Island member, corresponding to the late phase of Kansan glaciation, and an upper silt member, the Sappa member, corresponding to the latest Kansan phase of glaciation and in part to the Yarmouthian interglacial stage. The formation is classified as of late Kansan and Yarmouthian age.

Grand Island member--The basal gravel member of the Meade formation, the Grand Island member, is composed of granitic gravels that were deposited over most of the area by eastward-flowing streams. The valleys of Kansan age are generally broader and less deeply cut than those of Nebraskan age. Some of the deposits of the Meade formation are made up of locally derived material. Such deposits are found in tributary channels that connect to the main trunk streams of Kansan age.

The gravel of the tributary channels is mainly composed of material derived locally from Permian rocks, but it includes many fragments of caliche. The gravel resembles the Holdrege member of the Blanco formation except for the pebbles of caliche in the Grand Island member, which probably were derived from the Fullerton member of the Blanco formation. The Grand Island member ranges in thickness from a featheredge on the uplands in the south-central part of the county to as much as 100 feet in some of the deep channels. The Grand Island member in the uplands was deposited by a laterally shifting stream or streams flowing from the west.

Many wells in Reno County obtain water from the Grand Island member. The water is very hard in some areas and varies in quality from good to fair. Locally the water has been contaminated and is not suitable for use.

Sappa member--The Grand Island member of the Meade formation grades upward into the Sappa member, composed of sand: sandy silt, and silt. A lentil of volcanic ash known as the Pearlette ash is found in the lower part of the Sappa member. The Pearlette ash is present over an area extending from Iowa to Texas and is useful in identifying the Sappa member. The silt of the Sappa member is gray to tan or buff and contains many nodules of caliche in the upper part. The member ranges in thickness from a featheredge to 40 feet. The thickness is difficult to determine in much of the area because the Sappa member is overlain by the Loveland silt member of the Sanborn formation, which resembles the Sappa member very closely. During the Yarmouthian interglacial stage, a prominent soil was formed at the top of the Sappa member. This soil (Yarmouth soil) is overlain by younger eolian deposits in much of the area and is useful in identifying the upper limit of Kansan deposits. The Sappa member yields no water to wells in Reno County.

Sanborn Formation

Crete sand and gravel member--Illinoian Stage.--Sand and gravel assigned to the Crete sand and gravel member of the Sanborn formation are present in much of the western part of Reno County. These deposits have been observed above the Pearlette ash lentil of the Meade formation and below the Sangamon soil, which was developed at the top of the Loveland silt member. The Crete sand and gravel member ranges in thickness from a featheredge at the eastern edge of the deposit to as much as 40 feet in western Reno County. In part of the area the deposits are above the water table. In areas where the Crete sand and gravel member is below the water table, abundant supplies of water of good quality may be obtained.

Loveland silt member--Illinoian Stage.--Silts and clays of the Loveland silt member are present in north-central Reno County. The deposits range in thickness from a featheredge to as much as 15 feet. Thin deposits of the Loveland silt member are present in central Reno County and probably in much of the rest of the county, but where the member lies above the Sappa member of the Meade formation and where the Yarmouth soil is not present or at least is not exposed, the Loveland silt member cannot be distinguished easily from silts of the Sappa member. The Loveland silt member in Reno County is above the water table and yields no water to wells.

Terrace deposits--Wisconsinan Stage.--Terrace deposits classed as of Wisconsinan age are present in the major stream valleys in Reno County. These deposits probably represent the valley cutting and filling subphases of both early and late Wisconsinan glaciation. The terrace deposits are composed of sand, gravel, and silt, and small amounts of clay. They occupy the greater part of the valley area of the major streams and in Reno County are the principal sources of ground water. The deposits range in thickness from a featheredge along the sides of the valleys to as much as 130 feet in the valley of the Arkansas River near Hutchinson. The city of Hutchinson derives water from these deposits, as do many industrial users of water. The relatively smooth topography of the terrace areas is ideal for irrigation. The water from these deposits is hard but suitable for irrigation.

Peoria silt member--Wisconsinan Stage.--The Peoria silt member of the Sanborn formation represents the retreat phase of the glacial cycle. In Reno County thin deposits of the Peoria silt member overlie the Loveland silt member in the northern part of the county and probably mantle much of the county, but the member is not recognized easily. A period of soil formation took place after the deposition of the Peoria silt member. This period, named the Bradyan substage, was an interglacial phase of the glacial cycle. The Peoria silt member where present ranges in thickness from a featheredge to as much as 15 feet, lies above the water table, and yields no water to wells in Reno County.

Dune Sand--Wisconsinan and Recent Stages

Most of the western third of Reno County and the area between the Arkansas River and the Little Arkansas River are underlain by dune sand. The dune sand consists of uniform fine and medium sand, moderately well rounded, and, in some areas, includes silt and clay.

Two types of dune topography are recognized in Reno County. One type consists of moderately steep, irregular grass-covered hills surrounding shallow undrained basins. This type of topography is found mainly in the area between the Arkansas River and the Little Arkansas River and in small areas in the extreme western part of the county. The second type of dune topography consists of broader, lower swells and swales having a thicker soil; some of these areas have a rudimentary drainage.

Smith (1940, p. 159-165) described an ideal dune cycle of two phases: (1) an active or eolian phase during which the dune is built up, and (2) an elluvial or passive phase during which vegetation prevents more growth and the dune is subdued by weathering and creep. Smith divides the passive phase into three stages: youth, maturity, and old age. In the youthful stage the soil is developed and slopes are reduced; in the mature stage the dune becomes smooth and regular and the soil becomes more stable; and in old age the hills are no longer recognizable as dunes.

Most of the dunes in Reno County are in the passive phase, although a few dunes are in the eolian or active phase. Dunes in all stages of the passive phase are present in the county. The dunes in the area between the Arkansas River and the Little Arkansas River are mostly in the youthful stage, as are those in the northwestern part of the county. Boundaries between the different stages of dune sand are indistinct, as are the boundaries between the dune sand and older formations.

The thickness of the dune sand in Reno County ranges from a featheredge to as much as 120 feet.

In areas where the dune sand is not above the water table, wells obtain moderate supplies of water, the quality of which is good except that the iron content may be high (Table 5).

In the Arkansas River valley and the lower Cow Creek valley, the alluvium occupies channels cut into deposits of the Meade formation and terrace deposits of Wisconsinan age. The alluvium is similar to these deposits, as most of it is derived from them. It consists predominantly of coarse sand and gravel. Because of the similarity of the unconsolidated deposits in the valleys, their separation is difficult without fossil evidence. The unconsolidated deposits in the valleys of the Little Arkansas River and the Ninnescah River are of Recent age and, possibly, in part of Late Wisconsinan age and range in thickness from a featheredge to as much as 60 feet.

Many domestic and stock wells in Reno County obtain water from the alluvium. The water differs in quality from valley to valley, but generally it is hard. Nickerson is the only city in the county that obtains its water from alluvium. The water at Nickerson is very hard. The water from the alluvium in the Arkansas River valley and the Cow Creek valley is very hard and in some areas salty to the taste. The water is of poor quality and is generally undesirable for most municipal and industrial uses. The alluvial material in the Little Arkansas River valley is finer than that of the Arkansas River valley and the quality of the water is better than in the Arkansas River valley. In the Ninnescah River valley supplies of water are limited by the thinness of the alluvium, and the quality ranges from fair to poor.

Possibilities of Developing Additional Water Supplies

Ground-water supplies could be developed in much of Reno County for industrial and irrigation purposes. The potentialities for use of water for irrigation depend to a large extent on the topography, the type of soil to be irrigated, and the quality of water. Much of Reno County is not suitable for irrigation because of the local topography or the type of soil. The western third of the county is covered by sand dunes not suitable for irrigation except that dunes of the old-age stage in the alluvial phase and possibly some of the dunes in the mature stage might be irrigated by sprinklers. Much of the Arkansas River valley is level and suitable for irrigation, but there the soil in many places is not suitable, and the ground water has a high concentration of sodium. Large supplies of ground water could be developed in the Arkansas River valley for industrial uses, but the quality is poor; the chloride content and hardness are generally high.

Except in the terrace area at the foot of the sandhills, industrial or irrigation supplies of water generally cannot be obtained in most of the northeastern part of the county in the sandhill area. Gardens and orchards on the Wisconsinan terraces are irrigated to some extent. Many industrial wells in the east part of Hutchinson are in the terrace area. In the future, wells should be properly spaced to minimize lowering of the water table and induced infiltration of poor-quality water from the alluvium of Arkansas River south of the sandhills. Additional wells yielding 300 to 500 gallons a minute could be developed in these terrace deposits with proper spacing.

Water of good quality is found in the uplands just south of the Arkansas River. Two wells at the Hutchinson Naval Air Station southeast of Hutchinson, in the eastern part of the county, were both pumped at a rate of 365 gallons a minute for 21 hours with 15 feet of drawdown. With proper spacing, many wells having yields of 300 to 500 gallons a minute can be developed in this area. The quality of the water is good. The chloride content and hardness are low. Because the thickness of the water-bearing material diminishes southward (Fig. 23), a test-drilling program should precede the drilling of large-capacity wells.